The invention relates to a method of hermetically sealing a space, in which two or more boundary surfaces of a first space are interconnected by means of a thermo-setting glue and the curing operation is carried out in a second space.
The invention more particularly relates to a method of sealing in a moisture- and gas-tight manner, sensors, CCD's (Charge-Coupled Devices) and LCD's (Liquid Crystal Displays).
A method of the kind to which the present invention relates is known from JP 53-43477 (Kokai).
In this known method, a cavity in a substrate is closed by a covering plate, which plate is connected across the cavity to the substrate by means of a thermo-setting glue. The covering plate is provided with a hole through which gases can escape from the cavity. This is necessary because during the curing operation a pressure is built up in the closed cavity due to the temperature increase and gases tend to escape from the cavity due to this build-up of pressure. The hole is closed afterwards by means of another glue. If the covering plate should be glued to the substrate without being provided with a hole, ducts would be formed in the thermo-setting glue connection during the curing operation due to the escape of gases from the cavity. No hermetically sealing glue connection is then obtained.
Another method of the kind to which the present invention relates is known from JP 58-57879 (Kokai). In this known method, a cavity in a substrate is closed by a covering plate which plate is connected across the cavity to the substrate by means of two kinds of glue. The two glues are provided one beside the other and, after the first glue has cured at room temperature, the second thermo-setting glue is cured at elevated temperature. The gases which tend to escape from the cavity during the curing operation are stopped by the first glue bond and, after the second glue bond has cured, the cavity is sealed hermetically.
A disadvantage of these two methods is that additional laborious operations are necessary to obtain a hermetically sealing thermo-setting glue bond.
A hermetically sealing bond cannot be obtained by means of non-thermosetting glues because these glues are pervious to moisture.